Many video cameras use CMOS image sensors. Presently, most CMOS sensors capture video information using a rolling shutter technique. This technique entails capturing a frame of video information on a line-by-line basis, such as a row-by-row basis. More specifically, the rolling shutter technique begins the exposure of each line slightly after the exposure of a previous line. Further, the technique reads the video information for each line slightly after reading a previous line. In contrast, a global shutter technique exposes each line of a frame at the same time.
The temporally-staggered capture of video information in the rolling shutter technique can cause three main types of artifacts: (1) partial exposure; (2) shear or skew; and (3) wobble. Partial exposure occurs when a rolling shutter camera attempts to capture a fast-changing illumination, such as a flash, a strobe light, or lightning strike. Shearing occurs when the camera undergoes a constant (or smoothly varying) motion. Wobble occurs when the camera undergoes large accelerations, such as when the camera captures image information while mounted on a vehicle that undergoes high-frequency agitation. Wobble can also occur when the camera captures a scene that contains high-frequency motion.
In all categories of such artifacts, the camera is attempting to capture a frame of image information while a scene is undergoing a change (either because the scene is changing or the camera is being moved). Motion-related artifacts sometimes exhibit a so-called jelly effect, in which objects in the video information appears non-rigid (e.g., spatially warped). For example, straight lines in a scene appear as curved lines, which is particularly evident in the video information (in contrast to an individual frame).
Techniques exist for correcting artifacts attributed to shearing-type motion. For example, shearing can be corrected by computing a global motion associated with the video information and then warping its frames in an appropriate manner. But artifacts associated with high-frequency motion present a more complex problem, for which no satisfactory solution currently exists.